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Darja
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« Reply #2310 on: May 20, 2020, 03:46 AM »

Jupiter’s Biggest Moons Started as Tiny Grains of Hail

A new model offers an explanation for how the Galilean satellites formed around the solar system’s largest world.

By Shannon Stirone
NY Times
May 20, 2020

Konstantin Batygin did not set out to solve one of the solar system’s most puzzling mysteries when he went for a run up a hill in Nice, France. Dr. Batygin, a Caltech researcher, best known for his contributions to the search for the solar system’s missing “Planet Nine,” spotted a beer bottle. At a steep, 20 degree grade, he wondered why it wasn’t rolling down the hill.

He realized there was a breeze at his back holding the bottle in place. Then he had a thought that would only pop into the mind of a theoretical astrophysicist: “Oh! This is how Europa formed.”

Europa is one of Jupiter’s four large Galilean moons. And in a paper published Monday in the Astrophysical Journal, Dr. Batygin and a co-author, Alessandro Morbidelli, a planetary scientist at the Côte d’Azur Observatory in France, present a theory explaining how some moons form around gas giants like Jupiter and Saturn, suggesting that millimeter-sized grains of hail produced during the solar system’s formation became trapped around these massive worlds, taking shape one at a time into the potentially habitable moons we know today.

Dr. Batygin and Dr. Morbidelli say earlier theories explain only a part of how the solar system’s many objects formed. The two researchers set out to present the rest of the story with equations explaining how a new planet transitions from being surrounded by its disk of matter, to creating satellite building blocks, all the way to the formation of moons like Europa.

When Dr. Batygin and Dr. Morbidelli ran computer simulations of their proposed theory, they found that they’d accidentally re-created Jupiter’s small innermost moons as well as the four Galilean satellites, much as we see them today.

“I thought I was still dreaming when I saw the results,” Dr. Batygin said.

The equations amount to a recipe for how to make a moon. It starts with a mix of hydrogen and helium gas raining down onto Jupiter from above. Some of the gas gets swept out and away, spreading viscously as it goes into orbit around Jupiter in a process called decretion.

At this point in Jupiter’s formation, the only solid particles that orbited it were smaller than one millimeter across. Because this dust is very small — tiny grains about two parts ice to one part rock — it can couple itself to the gas washing away from Jupiter.

“The disk around Jupiter acts a little bit like a vacuum cleaner, where it sources small dust from the protoplanetary disk,” Dr. Batygin said.

As this material builds up over the course of about a million years, he says, it eventually reaches a mass that approximately matches Io, Europa, Ganymede and Callisto today.

The dust clumps together into a massive carpet of icy asteroids, some of which slow down, growing larger as they consume some of the other objects.

“Once the moon is big enough to ship, it gets on the conveyor belt,” Dr. Batygin said, and eventually moves in closer to Jupiter, parking into its orbit around the planet.

In this model, Io was formed in about 1,000 years and then quickly got ejected from the satellite feeding zone, leaving behind a mess of remaining icy asteroids in wonky orbits. Around 10,000 years later, Europa grows over about the course of a millennium and does the same thing. After a 30,000-year break, Ganymede begins to form, but takes 2,000 years to grow. Callisto, however, begins to form when the material from Jupiter is nearly depleted, so it takes much longer, around eight million years.

The model offers a similar explanation for Saturn and its largest moon, Titan: https://www.nytimes.com/2020/03/10/science/saturn-titan-moon.html

Jupiter and Its Moons: https://www.nytimes.com/interactive/2016/07/01/science/space/jupiter-and-its-moons.html?mtrref=www.nytimes.com&gwh=2A221FC9472000E5E59CAE1B3B28897C&gwt=pay&assetType=REGIWALL

Spinnable maps of Jupiter and the Galilean moons.

Jonathan Lunine, an astronomer at Cornell University who has studied the Galilean satellites’ formation, says the paper “sketches out a scenario more like the formation of the terrestrial planets,” than other theories. But he thinks that “it doesn’t solve head-on the curious fact that Ganymede, Callisto and Titan (Titan being the big moon of Saturn) all have very similar sizes and densities and yet totally different geologic histories.”

Closer study will be needed to fully explain these moons’ history. Luckily, missions planned to Saturn’s moon Titan and Jupiter’s moons Callisto, Europa and Ganymede in the next 20 years will yield more data to test theories like this one. And this research may aid our understanding about whether life is possible around other stars.

“If we’re going to find life, arguably the best place to look are the icy satellites of the giant planets,” Dr. Batygin said. If similar moons are likely to form around other stars’ gas giants, it raises the question of whether “life in the universe is actually pretty common” he said. “I don’t know, of course, but it’s an exciting thing to think about.”


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« Reply #2311 on: May 21, 2020, 03:36 AM »


Astronomers spot potential first evidence of new planet being born

Researchers observe swirling disc around AB Aurigae star, suggesting new world is forming

PA Media
21 May 2020 13.00 BST

Astronomers believe they may have found the first direct evidence of a new planet being born.

A dense disc of dust and gas has been spotted surrounding a young star called AB Aurigae, about 520 light years away from Earth.

Using the European Southern Observatory’s Very Large Telescope (VLT), located in Chile, the researchers observed a spiral structure with a “twist” near the centre, which suggests a new world may be in the process of forming. The swirling disc was one of the telltale signs of the star system being born in the constellation of Auriga, the scientists said.

Dr Anthony Boccaletti, who led the study from the Observatoire de Paris at the PSL University, in France, said: “Thousands of exoplanets have been identified so far, but little is known about how they form.”

He added: “We need to observe very young systems to really capture the moment when planets form.”

Until now astronomers had been unable to take clear images of young discs to see these twists.

Dr Boccaletti and his team of astronomers used VLT’s Sphere instrument to take photos of AB Aurigae, which show “a stunning spiral of dust” caused by the baby planet trying to “kick” the gas.

The same instrument was used in 2018 to take photos of another infant planet, thought to be just 5.4m years old.

According to Emmanuel Di Folco, of the Astrophysics Laboratory of Bordeaux (LAB), in France, and one of the study’s authors, this so-called kicking phenomenon causes “disturbances in the disc in the form of a wave, somewhat like the wake of a boat on a lake”.

As the new planet rotates around AB Aurigae, it causes the surrounding gas and dust to be shaped into a spiral arm. The very bright yellow region near the centre of the spiral is the twist, which lies at about the same distance from the star as Neptune from the sun.

Anne Dutrey of LAB, a study co-author, said: “The twist is expected from some theoretical models of planet formation. It corresponds to the connection of two spirals – one winding inwards of the planet’s orbit, the other expanding outwards – which join at the planet location.

“They allow gas and dust from the disc to accrete on to the forming planet and make it grow.”

The observations are reported in the Astronomy & Astrophysics journal.


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« Reply #2312 on: May 22, 2020, 03:38 AM »

This formula will ‘decode’ the habitability of exoplanets

By Mike Wehner
5/22/2020
BGR

    Scientists from Cornell University have developed a model to “decode” the habitability of distant exoplanets.
    By taking into account the color of the planet as it appears from a distance and the light of the start it is orbiting, scientists can calculate the likelihood that the surface is comfortable for life.
    New exoplanet-hunting telescopes will give researchers a better look at distant worlds, and with tools like this, we may get a better idea of which ones could host life.
   
In the endless search for worlds beyond our solar system, astronomers have discovered planets of many types, sizes, and circumstances. From frozen rocky worlds to massive, steaming gas giants orbiting so close to their star it’s a wonder they even still exist, exoplanets can vary dramatically. For scientists searching for life outside of Earth, it makes the job incredibly difficult, but astronomers at Cornell University have built a model that they think can help.

It’s a climate “decoder” of sorts, that gleans information about a planet’s potential for habitability based on the light that can be detected coming off of it. Their work was published in Monthly Notices of the Royal Astronomical Society, and it could exoplanet researchers focus their attention on worlds that have the best chance of supporting life.

Most exoplanets that astronomers discover don’t hold the possibilities of life. We know that because planets that orbit outside of the habitable zone of their star are either too cold to support liquid water on their surface or too hot to prevent it from boiling off. Additionally, gas giant planets aren’t thought to be candidates for life, so it doesn’t matter if those are found in the habitable zone or not.

However, when scientists detect rocky worlds within the habitable zone, things get a lot more interesting. There’s a surprising amount of information that can be gathered about a planet even when it sits many light-years away.

This new research effort takes into account data such as the color that the planet appears to be and the intensity of light from its host star. The combination of these data points can offer a clue as to the surface temperatures of the planet as well as its habitability for life as we know it.

“Depending on the kind of star and the exoplanet’s primary color—or the reflecting albedo—the planet’s color can mitigate some of the energy given off by the star,” Lisa Kaltenegger, co-author of the study, said in a statement. “What makes up the surface of an exoplanet, how many clouds surround the planet, and the color of the sun can change an exoplanet’s climate significantly.”

The scientists say that telescope projects that are currently in the works, including the Extremely Large Telescope, will give scientists an even better look at distant worlds, and that climate predictions for those exoplanets could prove valuable.


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« Reply #2313 on: May 23, 2020, 04:23 AM »


Four amazing astronomical discoveries from ancient Greece

on May 23, 2020
By The Conversation

The Histories by Herodotus (484BC to 425BC) offers a remarkable window into the world as it was known to the ancient Greeks in the mid fifth century BC. Almost as interesting as what they knew, however, is what they did not know. This sets the baseline for the remarkable advances in their understanding over the next few centuries – simply relying on what they could observe with their own eyes.

Herodotus claimed that Africa was surrounded almost entirely by sea. How did he know this? He recounts the story of Phoenician sailors who were dispatched by King Neco II of Egypt (about 600BC), to sail around continental Africa, in a clockwise fashion, starting in the Red Sea. This story, if true, recounts the earliest known circumnavigation of Africa, but also contains an interesting insight into the astronomical knowledge of the ancient world.

The voyage took several years. Having rounded the southern tip of Africa, and following a westerly course, the sailors observed the Sun as being on their right hand side, above the northern horizon. This observation simply did not make sense at the time because they didn’t yet know that the Earth has a spherical shape, and that there is a southern hemisphere.

1. The planets orbit the Sun

A few centuries later, there had been a lot of progress. Aristarchus of Samos (310BC to 230BC) argued that the Sun was the “central fire” of the cosmos and he placed all of the then known planets in their correct order of distance around it. This is the earliest known heliocentric theory of the solar system.

Unfortunately, the original text in which he makes this argument has been lost to history, so we cannot know for certain how he worked it out. Aristarchus knew the Sun was much bigger than the Earth or the Moon, and he may have surmised that it should therefore have the central position in the solar system.

Nevertheless it is a jawdropping finding, especially when you consider that it wasn’t rediscovered until the 16th century, by Nicolaus Copernicus, who even acknowledged Aristarchus during the development of his own work.

2. The size of the Moon

One of Aristarchus’ books that did survive is about the sizes and distances of the Sun and Moon. In this remarkable treatise, Aristarchus laid out the earliest known attempted calculations of the relative sizes and distances to the Sun and Moon.

It had long been observed that the Sun and Moon appeared to be of the same apparent size in the sky, and that the Sun was further away. They realised this from solar eclipses, caused by the Moon passing in front of the Sun at a certain distance from Earth.

Also, at the instant when the Moon is at first or third quarter, Aristarchus reasoned that the Sun, Earth, and Moon would form a right-angled triangle.

As Pythagoras had determined how the lengths of triangle’s sides were related a couple of centuries earlier, Aristarchus used the triangle to estimate that the distance to the Sun was between 18 and 20 times the distance to the Moon. He also estimated that the size of the Moon was approximately one-third that of Earth, based on careful timing of lunar eclipses.

While his estimated distance to the Sun was too low (the actual ratio is 390), on account of the lack of telescopic precision available at the time, the value for the ratio of the size of the Earth to the Moon is surprisingly accurate (the Moon has a diameter 0.27 times that of Earth).

Today, we know the size and distance to the moon accurately by a variety of means, including precise telescopes, radar observations and laser reflectors left on the surface by Apollo astronauts.

3. The Earth’s circumference

Eratosthenes (276BC to 195 BC) was chief librarian at the Great Library of Alexandria, and a keen experimentalist. Among his many achievements was the earliest known calculation of the circumference of the Earth. Pythagoras is generally regarded as the earliest proponent of a spherical Earth, although apparently not its size. Eratosthenes’ famous and yet simple method relied on measuring the different lengths of shadows cast by poles stuck vertically into the ground, at midday on the summer solstice, at different latitudes.

The Sun is sufficiently far away that, wherever its rays arrive at Earth, they are effectively parallel, as had previously been shown by Aristarchus. So the difference in the shadows demonstrated how much the Earth’s surface curved. Eratosthenes used this to estimate the Earth’s circumference as approximately 40,000km. This is within a couple of percent of the actual value, as established by modern geodesy (the science of the Earth’s shape).

Later, another scientist called Posidonius (135BC to 51BC) used a slightly different method and arrived at almost exactly the same answer. Posidonius lived on the island of Rhodes for much of his life. There he observed the bright star Canopus would lie very close to the horizon. However, when in Alexandria, in Egypt, he noted Canopus would ascend to some 7.5 degrees above the horizon.

Given that 7.5 degrees is 1/48th of a circle, he multiplied the distance from Rhodes to Alexandria by 48, and arrived at a value also of approximately 40,000km.

4. The first astronomical calculator

The world’s oldest surviving mechanical calculator is the Antikythera Mechanism. The amazing device was discovered in an ancient shipwreck off the Greek island of Antikythera in 1900.

The device is now fragmented by the passage of time, but when intact it would have appeared as a box housing dozens of finely machined bronze gear wheels. When manually rotated by a handle, the gears span dials on the exterior showing the phases of the Moon, the timing of lunar eclipses, and the positions of the five planets then known (Mercury, Venus, Mars, Jupiter, and Saturn) at different times of the year. This even accounted for their retrograde motion – an illusionary change in the movement of planets through the sky.

We don’t know who built it, but it dates to some time between the 3rd and 1st centuries BC, and may even have been the work of Archimedes. Gearing technology with the sophistication of the Antikythera mechanism was not seen again for a thousand years.

Sadly, the vast majority of these works were lost to history and our scientific awakening was delayed by millennia. As a tool for introducing scientific measurement, the techniques of Eratosthenes are relatively easy to perform and require no special equipment, allowing those just beginning their interest in science to understand by doing, experimenting and, ultimately, following in the foot steps some of the first scientists.

One can but speculate where our civilisation might be now if this ancient science had continued unabated.The Conversation

Gareth Dorrian, Post Doctoral Research Fellow in Space Science, University of Birmingham and Ian Whittaker, Lecturer in Physics, Nottingham Trent University

This article is republished from The Conversation under a Creative Commons license. Read the original article.


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« Reply #2314 on: May 25, 2020, 03:32 AM »

SpaceX ready to launch astronauts into space for the first time

on May 25, 2020
By Agence France-Presse

In the beginning, everyone was skeptical. But Elon Musk’s SpaceX defied expectations — and on Wednesday hopes to make history by ferrying two NASA astronauts into space, the first crewed flight from US soil in nine long years.

US President Donald Trump will be among the spectators at Kennedy Space Center in Florida to witness the launch, which has been given the green light despite months of shutdowns due to the coronavirus pandemic.

The general public, in a nod to virus restrictions, has been told to watch via a livestream as Crew Dragon is launched by a Falcon 9 rocket toward the International Space Station.

NASA’s Commercial Crew program, aimed at developing private spacecraft to transport American astronauts in to space, began under Barack Obama.

But his successor sees it as a symbol of his strategy to reassert American domination of space, both military — with his creation of the Space Force — and civilian.

He has ordered NASA to return to the moon in 2024, an unlikely timetable but one that has given the storied space agency a boost.

In the 22 years since the first components of the ISS were launched, only spacecraft developed by NASA and by the Russian space agency have carried crews there.

NASA used the illustrious shuttle program — huge, extremely complex, winged ships that carried dozens of astronauts into space for three decades.

But their staggering cost — $200 billion for 135 flights — and two fatal accidents finally put an end to the program.

The last shuttle, Atlantis, landed on July 21, 2011.

After, NASA astronauts learned Russian and travelled to the ISS in the Russian Soyuz rocket from Kazakhstan, in a partnership which survived political tensions between Washington and Moscow.

But it was only ever meant to be a temporary arrangement. NASA had entrusted two private companies — aviation giant Boeing and upstart SpaceX — with the task of designing and building capsules that would replace the shuttles.

Nine years later, SpaceX — founded by Musk, the outspoken South African entrepreneur who also built PayPal and Tesla, in 2002 — is ready to launch.

– ‘Success story’ –

At 4:33 pm (2033 GMT) on Wednesday, a SpaceX Falcon 9 rocket is set to take off from Launch Pad 39A with the Crew Dragon capsule at its top.

NASA has awarded SpaceX more than $3 billion in contracts since 2011 to build the spacecraft.

The capsule will be crewed by Robert Behnken, 49, and Douglas Hurley, 53, both veteran space travelers — Hurley piloted Atlantis on its last trip.

Nineteen hours later they will dock at the ISS, where two Russians and an American are waiting for them.

The weather forecast remains unfavorable, with a 60 percent chance of bad conditions, according to Cape Canaveral forecasters.

The next launch window is Saturday, May 30.

The launch has taken five years longer than planned to come about, but even with the delays SpaceX has beaten Boeing to the punch.

Boeing’s test flight of its Starliner failed due to serious software issues, and will have to be redone.

“It’s been a real success story,” Scott Hubbard, former director of NASA’s Ames Center in Silicon Valley who now teaches at Stanford, told AFP.

“There was huge skepticism,” Hubbard, who met Musk before the creation of SpaceX and also chairs a SpaceX safety advisory panel, recalled.

“Senior people at the legacy companies, Lockheed, Boeing, would tell me at a conference that these SpaceX guys don’t know what they don’t know,” he told AFP.

SpaceX finally came out on top with its cheaper Falcon 9 rocket, the first stage of which comes back to land vertically on a barge in the Atlantic.

Since 2012, SpaceX has been resupplying the ISS for NASA, thanks to the cargo version of the Dragon capsule.

The manned mission, called Demo-2, is crucial for Washington in two ways.

The first is to break NASA’s dependence on the Russians.

But the second is to catalyze a private “low Earth orbit” market open to tourists and businesses.

“We envision a day in the future where we have a dozen space stations in low Earth orbit. All operated by commercial industry,” said NASA boss Jim Bridenstine.

Musk is aiming higher: he is building a huge rocket, Starship, to circumnavigate the Moon — or even to travel to Mars and ultimately make humanity a “multi-planet species”.


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« Reply #2315 on: May 26, 2020, 03:30 AM »


China space program targets July launch for Mars mission

on May 26, 2020
By Agence France-Presse

China is targeting a July launch for its ambitious plans for a Mars mission which will include landing a remote-controlled robot on the surface of the red planet, the company in charge of the project has said.

Beijing has invested billions of dollars in its space program in an effort to catch up with its rival the United States and affirm its status as a major world power.

The Mars mission is among a number of new space projects China is pursuing, including putting Chinese astronauts on the moon and having a space station by 2022.

Beijing had been planning the Mars mission for sometime this year, but China Aerospace Science and Technology Corporation (CASC) has confirmed it could come as early as July.

“This big project is progressing as planned and we are targeting a launch in July,” CASC said in a statement issued on Sunday.

Called “Tianwen”, the Chinese mission will put a probe into orbit around Mars and land the robotic rover to explore and analyze the surface.

It will take several months to cover the roughly 55 million kilometers (31 million miles) distance between Earth and Mars, which is ever-changing due to their planetary orbits.

China has already carried out a similar mission to the Moon, and in January 2019 landed a small rover on the dark side of the lunar surface, becoming the first nation to do so.

The US, which has already sent four exploratory vehicles to Mars, intends to launch a fifth this summer. It should arrive around February 2021.

The United Arab Emirates plans to launch the first Arab probe to the Red Planet on July 15 from Japan.


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« Reply #2316 on: May 27, 2020, 03:43 AM »

Astronomers spot a galaxy shaped like a donut, and it looks delicious

By Mike Wehner
BGR
5/27/2020

    Scientists found a donut-shaped galaxy hiding out 11 billion light-years from Earth.
    The galaxy is making stars at an incredibly fast pace.
    Researchers believe it got its shape due to a collision with another galaxy.

Well, it looks like astronomers have finally found the absolute best possible thing they could ever hope to find when gazing deep into the cosmos. No, I’m not talking about alien life or the fountain of youth. Both of those things pale in comparison to the discovery recently revealed in a paper published in Nature Astronomy. Scientists found… a donut galaxy.

Okay, so maybe it’s just a big “cosmic ring of fire,” but it sure looks like a donut. And if it were a donut, I bet it would be absolutely delicious, especially if you dipped it in the Milky Way. (Get it?)

Seriously though, the discovery is pretty cool. The galaxy, named R5519, sits a whopping 11 billion light-years from Earth. That means that what we see when we’re looking at it is how the galaxy looked 11 billion years ago. It’s absolutely ancient to our eyes, and it’s a real weirdo as far as galaxies go.

“It is a very curious object that we’ve never seen before,” Dr. Tiantian Yuan, lead author of the study, said in a statement. “It looks strange and familiar at the same time.” Yeah, it looks familiar because it’s what I ate for breakfast this morning.

And what exactly is this bizarre galaxy doing right now? Or, should I say, what was it doing 11 billion years ago? Churning out stars like some kind of overstaffed factory. “It is making stars at a rate 50 times greater than the Milky Way,” Yuan says. “Most of that activity is taking place on its ring – so it truly is a ring of fire.”

As for how it formed, the researchers believe it didn’t initially form as a ring at all. Some ring galaxies appear to have formed on their own without outside influence, but not R5519. The researchers believe this is one rare example of a “collisional ring galaxy.”

The name sort of gives it away, but a collisional ring galaxy forms due to dust-ups with other galaxies. It’s incredibly rare to see one like this, and it’s even rarer to see one that is so old. It’s cool to look at, but it’s also helping astronomers better understand the intricacies of galaxy formation.

“In the case of this ring galaxy, we are looking back into the early universe by 11 billion years, into a time when thin disks were only just assembling,” study co-author Kenneth Freeman said in a statement. “For comparison, the thin disk of our Milky Way began to come together only about nine billion years ago. This discovery is an indication that disk assembly in spiral galaxies occurred over a more extended period than previously thought.”

It still looks pretty tasty to me.


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« Reply #2317 on: May 28, 2020, 03:30 AM »

Why is our galaxy’s black hole blinking at us?

By Mike Wehner
May 28th, 2020
BGR

    The black hole at the center of our galaxy is blinking at us, and scientists think they know why.
    In a new researcher paper, astronomers explain that a disk of material surrounding the black hole may be producing flashes due to “hot spots” that form within it.
    The research was published in Astrophysical Journal Letters.

The Moon revolves around the Earth, Earth revolves around the Sun, and the Sun — along with everything else in our galaxy — revolves around a supermassive black hole that sits at the very center. It’s a dance that began long before we got here, but scientists are doing their best to make up for the lost time by explaining how black holes work, why they exist, and what they can teach us about the formation of the universe.

Now, researchers using data from the Atacama Large Millimeter/Submillimeter Array (ALMA) telescope operated by the European Southern Observatory in Chile have documented a puzzling phenomenon happening near the location of Sagittarius A*, the location at the heart of the Milky Way believed to be a black hole. It seems that the supermassive black hole is blinking in our direction.

In a new paper published in The Astrophysical Journal Letters, researchers describe their observations of rapidly-flickering light curves coming from the location of Sgr A*. Black holes themselves don’t glow or emit light, so what could it possibly be?

“It has been known that Sgr A* sometimes flares up in millimeter wavelength,” Yuhei Iwata, lead author of the paper, said in a statement. “This time, using ALMA, we obtained high-quality data of radio-wave intensity variation of Sgr A* for 10 days, 70 minutes per day. Then we found two trends: quasi-periodic variations with a typical time scale of 30 minutes and hour-long slow variations.”

For all the discoveries scientists have made about our universe and our place in it, we still know precious little about black holes. That’s understandable, especially considering they’re invisible in visible light (they have a habit of swallowing it) and it’s not easy to study something you can’t even see.

However, due to the intensity of the gravitational pull of black holes, they tend to be surrounded by material that they are slowly slurping up. Hot gasses, dust, and debris form a halo around the black hole known as an accretion disk. Matter within the disk can move at speeds that approach the speed of light.

The flickering emissions are thought to be originating within an area of the disk nearest the black hole itself. Hot spots which can form within the fast-moving disk and, the scientists think, it’s the emissions from these hotspots that appear to “blink” at us when they are moving toward us in their orbit of the black hole.

“Hot spots are sporadically formed in the disk and circle around the black hole, emitting strong millimeter waves,” the researchers explain in a press release. “According to Einstein’s special relativity theory, the emission is largely amplified when the source is moving toward the observer with a speed comparable to that of light.”


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« Reply #2318 on: May 29, 2020, 03:28 AM »

How Europe’s CHEOPS satellite will improve the hunt for exoplanets

on May 29, 2020
By The Conversation

While the planet has been on lockdown the last two months, a new space telescope called CHEOPS opened its eyes, took its first pictures of the heavens and is now open for business.

The CHEOPS mission adds a unique twist in the science that the public normally associates with planet discovery missions like Kepler and TESS. Kepler and TESS produced many groundbreaking discoveries and brought the number of known exoplanets into the thousands – so many that we’ve only scratched the surface of what we can learn from them. Consequently, rather than simply finding more planets, the primary objective of CHEOPS is to better understand the planets that we’ve already found.

I have been in the exoplanet field for the better part of two decades. For most of that time I had the good fortune to work on NASA’s Kepler mission. Among Kepler’s major discoveries is the baffling array of planets that it found. Two prime examples are the thousands of planets whose sizes fall in the gap between Earth and Neptune. Kepler also found planets with orbits that are only a few hours long. None of these planets has counterparts in the solar system. What these planets are like, how they form and how they arrived at their current state are matters of ongoing research. To better understand these planets, we need to have better measurements of their properties – their sizes, masses, composition and atmospheres. Astronomers will turn to CHEOPS to fill these gaps in our knowledge.
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CHEOPS mission overview

A joint Swiss-ESA mission, CHEOPS, the “Characterizing Exoplanet Satellite,” will make key measurements of the size and albedo (reflectivity) of planets that orbit distant stars. CHEOPS launched in December of 2019 from the northern coast of South America, hitching a ride as a secondary passenger on a big Soyuz rocket.

The challenge with most of the planets discovered by the Kepler mission is that they orbit faint stars, making them difficult to observe with any telescope other than Kepler itself (which has finished its work and is no longer operating). CHEOPS, on the other hand, will observe planets orbiting bright stars that haven’t been studied with the level of detail once provided by Kepler, and that CHEOPS is now able to provide. These planets are more amenable to the wide variety of complementary observations from instruments on other telescopes – giving new insights into the nature of these recently discovered planets.

CHEOPS was placed in a “Sun-synchronous” orbit where it stays constantly above the Earth’s terminator – the line on the Earth that separates day from night. The satellite observes planets as they transit in front of their host stars using a 32-centimeter mirror. The telescope is 10 times smaller than Kepler, but since it will observe brighter stars, it can achieve a precision similar to Kepler – a fact demonstrated during its commissioning stage. And instead of continuously (and simultaneously) observing a hundred thousand stars in order to discover new planets, CHEOPS looks at individual targets when and where the planet is known to be there.

For the brightest Sun-like stars, CHEOPS can measure the sizes of planets as small as the Earth by seeing the fraction of the starlight that is blocked by the planet as it passes in front of the star. The improved measurements of planet sizes allow scientists to determine a planet’s density, giving insights into its composition and interior structure. They also establish the key relationship between planetary sizes and their masses, which tells us more about the traits shared by planets across many systems.

In addition to planet sizes, CHEOPS can measure a planet’s “phase curve,” the variation in brightness due to the changing profile of the planet as it orbits its host star (like the changing phases of the Moon). The phase curve tells us how much light is reflected by the planet and, therefore, some of the properties of its surface, atmosphere and clouds. This information, in turn, can tell us more about the conditions that might exist under the cloud tops and at a planet’s surface. Finally, since CHEOPS targets are bright, they are good candidates for detailed observations of their atmospheres using large ground-based and space-based telescopes (like the Extremely Large Telescope and the James Webb Space Telescope).

Ultimately, by better understanding the properties of planets orbiting other stars, astronomers can better understand the nature of the planets in our own solar system. We will better see how our planetary siblings fit into the broader context of planets in the galaxy and how our formation and history is similar to, or different from, these alien worlds.

[You’re smart and curious about the world. So are The Conversation’s authors and editors. You can get our highlights each weekend.]The Conversation

Jason Steffen, Assistant Professor of Physics and Astronomy, University of Nevada, Las Vegas


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« Reply #2319 on: May 30, 2020, 04:30 AM »

Scientists explain mysterious ‘lava flows’ on Mars

By Mike Wehner
BGR
2020

    Volcano-like features on Mars may actually be the result of mud flows rather than lava, researchers now say.
    Using simulated Mars conditions, researchers were able to create mud flows that look a lot like cooled lava flows.
 
You don’t have to be a space science fan to realize that Mars is everyone’s obsession right now. Both NASA and the ESA are poised to send missions to the Red Planet (though the ESA will now be waiting until 2022 to do so), and scientists are studying every aspect of the planet’s geology, climate, and even how often it shakes.

One of the more interesting observations that captured the imaginations of Mars researchers is what appears to be lava flows on the surface. The shape of these landforms makes them look a lot like cooled lava which oozed out of the surface long ago, but an international team of researchers now has a different explanation, and it might be even more interesting than flowing lava.

In a new paper published in Nature Geoscience, researchers explain that it’s not lava erupting out of the ground and flowing slowly along the surface, but mud. Yep, mud.

“Large outflow channels on ancient terrains of Mars have been interpreted as the products of catastrophic flood events,” the researchers explain. “The rapid burial of water-rich sediments after such flooding could have led to sedimentary volcanism, in which mixtures of sediment and water (mud) erupt to the surface. Tens of thousands of volcano-like landforms populate the northern lowlands and other local sedimentary depocentres on Mars.”

Proving that the tiny “volcanoes” are mud and not ancient liquid rock isn’t easy, but the scientists conducted experiments to determine whether or not it was possible for such mudflows to happen on the chilly Martian surface. On Earth, flowing mud just runs along and slowly dries, but on Mars it actually freezes, and that causes it to behave a lot differently.

“We found that low viscosity mud under Martian conditions propagates differently from that on Earth, because of a rapid freezing and the formation of an icy crust,” the scientists explain. “Instead, the experimental mud flows propagate like terrestrial pahoehoe lava flows, with liquid mud spilling from ruptures in the frozen crust, and then refreezing to form a new flow lobe. We suggest that mud volcanism can explain the formation of some lava-like flow morphologies on Mars, and that similar processes may apply to cryovolcanic extrusions on icy bodies in the Solar System.”

It’s an incredibly interesting theory, and it makes a lot of sense on a place like Mars. We know Mars has ice and water, at least at certain times of the year, and frozen mud extrusions could easily explain the features we now see on the surface.


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« Reply #2320 on: Jun 01, 2020, 03:38 AM »

Nasa proposals to allow establishment of lunar 'safety zones'

US accused by Russia of trying to circumvent 1967 treaty banning ownership of areas of the moon
Artist’s impression of lunar exploration at the south pole crater.

Guardian
6/1/2020

ountries joining Nasa’s exploration of the moon will be asked to sign up to a series of guiding principles known as the Artemis accords. Announced on 15 May, the accords are a set of broad themes that the agency hopes will form the basis of agreements to be negotiated with each country involved in the effort to land the next humans on the moon by 2024.

Based in part on the UN’s outer space treaty of 1967, the Artemis accords reassert that all activities should be undertaken only for peaceful purposes, and add that all plans should be communicated transparently with no secrecy. They commit the partners to using open international standards to allow machinery and equipment to function easily together, to provide emergency assistance to other astronauts and to mitigate the creation of space debris.

Where the accords are likely to become controversial is that they appear to allow the use of lunar resources for commercial gain, and they seek to establish “safety zones” around landing sites, which could be interpreted as de facto ownership of areas of the moon, which is forbidden by the outer space treaty. Dmitry Rogozin, the head of Russia’s space agency, Roscosmos, has accused the US of trying to circumvent the UN with the accords.


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« Reply #2321 on: Jun 02, 2020, 03:55 AM »

The Sun is going quiet as we dive deeper into a solar minimum

By Mike Wehner
BGR
6/2/2020

    Solar activity is waning, and scientists say we’re headed into a period of low Sun activity known as the solar minimum.
    The Sun follows a pattern of active and not-so-active periods on a cycle that lasts approximately 11 years.
    The previous solar maximum peaked in 2014, and it was historically mild, suggesting that the solar minimum we’re entering may be even quieter than usual.
 
If you gazed up at the Sun today (indirectly, to avoid severe eye damage) it would look like it’s always looked. It’s big, incredibly bright, and warm. Scientists, on the other hand, see the Sun in an entirely different light (pun partially intended), and based on their observations so far in 2020, our star is going quiet.

Researchers that keep an eye on Sun activity — like the fine folks at Spaceweather.com — have noticed a dramatic decrease in the number of quiet days so far this year. The Sun has already racked up over three months’ worth of days without a single sunspot, which is a huge indicator that the Sun is entering a period known as the solar minimum.

We don’t really notice it from our place here on Earth unless we’re looking for it with special instruments, but the Sun isn’t the same year after year. In fact, it changes quite a bit over the course of a decade. On average, a solar cycle takes 11 years, shifting between the solar minimum — characterized by a decrease in sunspots, solar flares, and magnetic field activity on the Sun — and the solar maximum, which is the exact opposite.

The most noticeable change for us here on Earth is increasing aurora activity during the solar maximum, as well as an increased chance of satellite communication disruptions when the Sun launches charged particles in our general direction.

Solar minimums aren’t typically anything to worry about. The energy output of the Sun is almost indistinguishable during periods of solar minimum, with a dip of a fraction of a percent at most.

There has historically been speculation regarding whether a particularly deep and extended solar minimum called the Maunder Minimum in the 1600s contributed to the Little Ice Age, which was a period of colder-than-average temperatures across both North America and Europe, but the evidence is weak. It’s more likely, some scientists suggest, that the temperature dip was linked to volcanic activity rather than a quiet solar period. Overall temperatures are believed to have dropped just 1 degree on average during that mini “ice age.”

You’ll probably still see talk of scientists “warning” us about a solar minimum, especially since the previous solar maximum peaked in 2014 was historically mild, but generally speaking there’s no reason to be concerned that this particular cycle will be anything out of the ordinary.


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« Reply #2322 on: Jun 03, 2020, 03:26 AM »

Europa’s hidden ocean supported by decades-old data

By Mike Wehner
BGR
6/3/2020

    Jupiter’s moon Europa may have a vast ocean of water beneath its surface, and new data from Galileo supports that theory.
    Researchers found that a lack of protons over Europa’s north pole could indicate an active water plume.
    Tidal forces prevent the water from freezing, but whether life exists there remains a mystery.
   
Jupiter’s moon Europa is an incredibly interesting place. It’s a massive ball of ice that scientists believe is hiding a vast ocean of liquid water. Proving that there’s water buried beneath the crust is tricky, but a new study reveals that data gathered two decades ago supports that theory.

As Gizmodo reports, a new paper published in Geophysical Research Letters focuses on readings taken by NASA’s Galileo spacecraft way back in 2000. During that mission, Galileo’s Energetic Particle Detector was constantly on the lookout for charged particles moving rapidly through space. When the spacecraft cruised over Europa’s north pole, its particle detector noted a dearth of protons.

At first, scientists studying the data couldn’t explain why and attributed the odd data to Europa possibly hindering the instrument and preventing it from detecting the particles. Now, with hindsight in their favor, researchers came up with a different and extremely exciting explanation.

More recent observations of Europa by the Hubble Space Telescope revealed what appears to be plumes of water being blasted into space. In simulating the conditions of Europa’s atmosphere and the plume of water vapor, the researchers discovered that the lack of protons during Galileo’s flyby is likely evidence that it passed by an active plume.

“What is new here is that part of the decrease can be explained by charge exchange, a process whereby the protons are removed after they lose their electrical charge in Europa’s thin atmosphere,” the researchers explain. “Furthermore, we see that there is a special decrease, which can be explained by an erupting plume of water vapor, thereby providing additional evidence for an active plume during Galileo flyby E26.”

It was long believed that icy worlds like Europa and Saturn’s Enceladus were solid. More recently, scientists have offered explanations of how water in liquid form could still exist deep beneath the frozen crust. Tidal forces from their host planets provide enough energy to keep the water from fully freezing, and cracks in the icy crust allow some of that liquid to spew into space.

Of course, the big question still remains: If these icy moons have vast oceans hiding inside, does that mean life could exist there? We simply don’t know. It would be mighty dark in those subsurface oceans, but as we’ve seen on our own planet, life can still exist in an absence of sunlight. Future missions could reveal the secrets hiding within Europa and Enceladus, but for now, we’ll just have to wait and wonder.


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« Reply #2323 on: Jun 04, 2020, 03:13 AM »


Astrophysicists destroy virtual stars to simulate the birth of black holes

No real stars were hurt...

Tibi Puiu
BGR
6/4/2020

By employing the resources of one of the fastest supercomputers in the world, astrophysicists in Australia have simulated the last days of very large stars with masses many times that of the Sun. Their simulation provides new valuable insights into how massive stars end with a bang as they explode in supernovae events and how black holes and neutron stars rise out of the ashes.

Cosmic chaos inside a computer chip

The state-of-the-art OzSTAR supercomputer at the Swinburne University of Technology crunched the numbers for various simulations that modeled the core-collapse of three stars. These virtual stars are 39, 20, and 18 times more massive than the sun, respectively.

When such massive stars reach the end of their life cycles, they typically experience a core-collapse supernova. When this happens, they turn into some of the brightest objects in the universe. And, in the aftermath, they are ready to become neutron stars or black holes.

This extremely dramatic stellar death also generates gravitational waves, whose signature can inform astrophysicists about how both black holes and neutron stars are birthed — this was the main aim of this simulation.

For instance, in 2017, astronomers detected a cosmic cataclysmic event: The merger of two neutron stars from 130 million years ago. The force of the collision was so strong that it literally shook the fabric of space-time, generating gravitational waves that eventually reached Earth, where they were detected. The two neutron stars either merged into a huge single neutron star or collapsed into a black hole.
A 3D-volume render of a core-collapse supernova. Credit: Bernhard Mueller, Monash University.

But in order to detect various core-collapse supernovae from gravitational waves, scientists need to know what such signals will look like.

The new simulation modeled complicated physics, informing scientists what kind of signals they should expect to see in their detectors when a star explodes.

    “Our models are 39 times, 20 times, and 18 times more massive than our sun. The 39-solar mass model is important because it’s rotating very rapidly, and most previous long-duration core-collapse supernova simulations do not include the effects of rotation,” said Jade Powell, a postdoctoral researcher at OzGrav.

According to the results, which were described in the Monthly Notices of the Royal Astronomical Society, the two most massive virtual stars generated explosions powered by neutrinos, while the smallest virtual star didn’t explode at all.

Such stars that don’t go fully supernova emit lower amplitude gravitational waves, but their frequency is still within detectable ranges of current detectors in use.

The findings also suggest that exploding stars producing large gravitational-wave amplitudes could be detected by the next generation of detectors, such as the upcoming Einstein Telescope.

    “For the first time, we showed that rotation changes the relationship between the gravitational-wave frequency and the properties of the newly-forming neutron star,” explains Powell.


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« Reply #2324 on: Jun 05, 2020, 03:25 AM »

Did Mars once have rings? Scientists say it’s possible

By Mike Wehner
BGR
6/5/2020

    Mars may have once had rings, and researchers say the evidence may still be orbiting the planet today.
    Phobos, the tiny Martian moon, may have once been much larger, slowly getting closer to Mars until it was torn to shreds and formed a ring of dust and debris.
    That ring may have then coalesced into a moon once again, and this pattern could have repeated several times in the history of our solar system.

We think of Mars today as a big, mostly barren orange rock. It’s like Earth if Earth had its atmosphere stripped away and had to endure billions of years of erosion as it lost its water to space. Long ago, Mars looked a lot different. It was wet, and perhaps even supported life in some form. According to new research presented at a recent meeting of the American Astronomical Society, it might have also sported rings.

But how could we possibly know whether or not Mars had rings billions of years ago? Surely the evidence of the rings is long gone, right? Maybe not. The researchers behind the study suggest that the strange Martian moons Deimos and Phobos may explain a cycle of ring creation and destruction around Mars.

First, the scientists began with what they know based on data and observations of Phobos. Phobos is gradually falling closer and closer to the Martian surface. It’s happening very slowly, but eventually, it will get too close to remain intact and the gravitational pull of the planet and the speed of the moon in orbit will cause it to be torn to pieces.

Some of those pieces may fall to the surface, but much of the debris could continue to orbit Mars, with chunks crashing into each other, generating dust, and spreading out into a true planetary ring. Even more interesting, it’s possible that the ring could eventually reform into a moon, and the scientists say that it’s possible this has already happened to Phobos in the past, cycling between moon and ring at different stages of its life and getting smaller every time.

Okay, so Phobos might eventually turn into a ring, but how does that hint at past rings? Well, Deimos, another Martian moon, has a very odd orbit. It doesn’t circle the planet on the same plane as Phobos and instead has an inclined orbit that scientists have never fully explained. The researchers suggest that Deimos’ unique orbital characteristics are actually the result of some other large body interacting with it.

That object may have been an entirely different early moon or perhaps an earlier version of Phobos. A much larger version of the now-tiny moon could have easily affected the orbit of Deimos and pushed it into the strange orbit it now enjoys.


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